In image forming devices, such as electrophotographic printers, an electrostatic latent image is formed on a uniformly-charged surface of a photosensitive drum by exposing the surface by light from an exposure unit. When a developer is supplied onto the electrostatic latent image, a developer image is carried on the surface of the photosensitive drum. The developer image is then transferred onto a sheet of paper. In this manner, an image is formed on a sheet of paper.
In some of the image forming devices, an LED (light-emitting diode) array head is provided as the exposure unit, and a process cartridge having the photosensitive drum is detachably mounted to a device main body. The LED array head has a plurality of LEDs arranged in an axial direction of the photosensitive drum, and is disposed in close vicinity to and in opposition to the surface of the photosensitive drum. The LED array head irradiates light from each LED, without going through a reflecting mirror, on the surface of the photosensitive drum. Because the LED array head is in close vicinity to the surface of the photosensitive drum, the LED array head forms an obstacle to attachment or detachment of the process cartridge. Thus, in the image forming device with such configuration, a mechanism for moving the LED array head toward or away from the surface of the photosensitive drum is essential.
Japanese Patent-Application Publication No. 2004-167728 proposes to attach an LED head to an inner surface of a cover that opens or closes an upper surface of a main casing so that the LED head is moved toward or away from a surface of a photosensitive drum in association with the closing and opening of the cover.
However, in this configuration, it is necessary to ensure a large space for opening the cover above the main casing. Thus, such an image forming device is unsuitable for installation on a location, such as on a shelf, having a limited space in the vertical direction.
In an image forming device proposed by Japanese Patent-Application Publication No. HEI-5-249767, an outer cover is provided on a front surface of a main casing, and an LED array head is attached to a holder that rotates in association with the opening or closing of the outer cover, moving the LED array head toward or away from a surface of a photosensitive member
This configuration does not require a large space above the image forming device since the outer cover is provided on the front surface of the main casing. However, this configuration requires the holder to be long in the vertical direction. This configuration also requires a mechanism for linking opening or closing of the outer cover to the rotation of the holder Thus, the dimension of the image forming device especially in the vertical direction cannot be reduced. For his reason, the image forming device proposed in Japanese Patent-Application Publication No. HEI-5-249767 also is unsuitable for installation on a location with a limited space in the vertical direction.